Stereoselective syntheses of 4-hydroxy 4-substituted glutamic acids

The 4-hydroxy 4-substituted glutamic acid moiety is a common substructure of biologically important natural products such as monatin [(2S,4S)-2], lycoperdic acid (3), and dysiherbaine (4). To develop methodology for syntheses of these natural products, cycloadditions of nitrone 5 with 2-substituted 2-propen-1-ols 6 and 2-substituted acrylates 8 were investigated. Reactions of nitrone 5 with alcohols 6 in the presence of MgBr2OEt2 gave cycloadducts 7 in a highly stereoselective manner, whereas noncatalyzed reactions of 5 with acrylates 8 afforded adducts 9. Using the former reaction, syntheses of monatin [(2S,4S)-2], monatin derivative 18, and lycoperdic acid (3) were accomplished. The C4-epimer of monatin [(2S,4R)-2)] was also synthesized by employing the latter cycloaddition.     

Radiation chemical studies of protein reactions: Effect of irradiation liquid containing aromatic hydrocarbons and pH on viscosity

When protein is irradiated by γ-rays from a ⁶⁰Co source in various liquids containing aromatic hydrocarbons, such as benzene, naphthalene, and phenanthrene, the effect of the radiation varies with the irradiation liquids containing aromatic hydrocarbons. An empirical equation for the viscosity change was obtained. Protein irradiated by γ-rays from a ⁶⁰Co source in air showed the effect of pH on protein reactions. An empirical equation for the viscosity change was obtained.     

522—Catalytic oxydation of biological components on platinum electrodes modified by adsorbed metals: Anodic oxidation of glucose

The catalytic oxidation of glucose on Pt electrodes modified by adsorbed metals was studied in 1 M HClO₄ by linear sweep voltammetry. The adsorbed metals (denoted as M_ad, such as Bi_ad and Pb_ad) formed on Pt in the potential region more positive than the reversible potential of an M⁼⁺/M^o couple, lead to a marked increase in the anodic c?urrent of glucose by about one order of magnitude. The catalytic activity depends on the surface coverage by the M_ad. The strongly adsorbed species of lactone type, which are responsible for blocking the successive oxidation, are formed on the electrode surface in the anodic processes of glucose on a bare Pt electrode. The formation of such poisonous species is accelerated in the presence of adsorbed hydrogen on Pt. The effects of M_ad were discussed on the basis that M_ad plays its major role on the Pt electrode surface in removal of the adsorbed hydrogen which initiates the formation of the poisonous species.     

Catalytic effects of metal submonolayers formed by faradaic adsorption on the anodic oxidation of ascorbic acid at a platinum electrode

The catalytic effects of metal ions on the anodic oxidation of ascorbic acid on a Pt electrode in 1 M HClO₄ were studied by linear sweep voltammetry. The anodic peak due to a two-electron oxidation of ascorbic acid shifts to the negative potential side on the addition of Bi³⁺. This indicates the accelerating effect of Bi³⁺ on the oxidation of ascorbic acid. The presence of other metal ions, such as Pb²⁺, Hg²⁺, Tl⁺, Ag⁺ and Sb³⁺, also exerts similar effects. These metal ions were adsorbed on a Pt electrode at underpotentials and the adsorbed metals (denoted as M_ad) still remain on the electrode surface until the electrode potential goes up to and beyond the peak potential of the oxidation of ascorbic acid. On the other hand, metal ions forming no adsorbed layer on Pt, such as Co²⁺, Zn²⁺, Fe³⁺ and Ni²⁺, exhibit no catalytic effect. These facts suggest that the presence of a M_ad on Pt is essential for the promotion of the anodic oxidation of ascorbic acid. However, there is a difference in the catalytic action among the M_ad, for example, Cu_ad, Cd_ad, In_ad, Sn_ad and Mo_ad display no catalytic action.The catalytic activity depends on the degree of surface coverage by the M_ad. The maximal effect of the M_ad is attained in the submonolayer region. The effects of metal ions were discussed on the basis that the M_ad plays its major role in the removal of the adsorbed ascorbic acid occupying active sites on the electrode surface, and provides effective sites for the activation of adjacent water molecules. Furthermore, from the ¹³C NMR spectra for the oxidation products, the adsorbed water on the M_ad appears to function by promoting the subsequent hydration steps, following the electron-transfer step of ascorbic acid.     

Radiation Chemical Studies of Protein Reactions: Effect of Amino Acids,Proteins, Vitamins,Chelating Agents,S-Containing Compounds,and Temperature on Viscosity

Amino acids, proteins, vitamins, chelating agents, and S-containing compounds were found to protect the shape of the external envelope of the protein molecule from radiation damage. The behavior of the viscosity change closely resembles that found with sodium glutamate and sodium benzoate, as shown by a similar dependence on the concentration. Protein irradiated by γ-rays showed the effect of temperature on changes in the shape of the external envelope of the protein molecule. The behavior of the viscosity change was studied.     

Radiation Chemical Studies of Protein Reactions: Effect of Chelating Agents on the Breaking of Secondary Bonding in Protein

The radiation protective effect of the breaking of secondary bonding in proteins was examined with 1,2 diamine and 1,2 dihydroxy derivatives such as ethylenediamine, ethylenediaminetetraacetic acid, and propylene glycol, and monosubstituted amines and alcohols such as ethylamine and n-propyl alcohol. An empirical equation for the viscosity change was obtained.     

Radiation Chemical Studies of Protein Reactions: Effect of Irradiation Liquids Containing Aromatic Hydrocarbons and pH on Optical Rotation

When protein in various liquids containing aromatic hydrocarbons, such as benzene, naphthalene, and phenanthrene, is irradiated by γ-rays from a ⁶⁰Co source the changes in the internal relationships of the atoms in the protein molecule vary with the irradiation liquids containing aromatic hydrocarbons. An empirical equation for the optical rotation was obtained, and the phenomena were explained on the basis of the molecular mechanism. Protein irradiated by γ-rays from a ⁶⁰Co source in air showed the effect of pH on the changes in the internal relationships of the atoms in the protein molecule. An empirical equation for the optical rotation was obtained, and the phenomena were explained on the basis of the molecular mechanism.     

Absorption Spectrum of H2O in the Range 12 400-14 520 cm

Fourier transform spectra recorded using (a) natural abundance water vapor, (b) H₂¹⁸O-enriched water vapor, and (c) H₂¹⁷O-enriched water vapor are analyzed. The ratio of intensities in three spectra is used to identify 927 lines due to absorption by H₂¹⁸O. Intensities and self-broadening parameters are derived for these lines. Using theoretical linelists, comparisons with previously assigned H₂¹⁶O spectra, and automatic searches for combination differences, 747 lines are assigned. These lines belong to 14 vibrational states in the 3ν+δ and 4ν polyads. Newly determined H₂¹⁸O vibrational band origins include 4ν₁ at 13 793.09 cm⁻¹, 3ν₁+ν₃ at 13 795.40 cm⁻¹, 2ν₁+2ν₃ at 14 188.82 cm⁻¹, ν₁+3ν₃ at 14 276.34 cm⁻¹, and 2ν₂+2ν₂+ν₃ at 13 612.71 cm⁻¹. These results are compared with data in HITRAN.